A band spectrum of tin monochloride exhibiting isotope effects

Abstract

The present paper is an extension of the work on the band spectra of chlorides of elements of Groups III and IV already published, and deals with a hitherto unrecorded band spectrum developed by the uncondensed discharge through the vapour of tin tetrachloride. In the cases of CCl 4 , SiCl 4 , TiCl 4 , BCl 3 and A1Cl 3 the uncondensed discharge through the vapour of the chloride alone develops bands which may be ascribed to a chloride of the element, while the addition of oxygen to the vapour results in the suppression of these chloride bands and the development of an oxide spectrum. As results from the present investigation, the addition of oxygen to the SnCl 4 vapour does not appear to quench the new chloride band spectrum and produce the oxide spectrum recorded by other observers; the analogy between the case of SnCl 4 and those of the other chlorides mentioned, thus appears at present to be incomplete. The new investigation has, however, led to other very interesting results; for it has been possible to arrange a large majority of the heads of the new tin chloride bands into two systems, to assign vibrational quantum numbers to the bands in each system, to attribute the two systems definitely to tin monochloride, SnCl, and to recognise the chlorine isotope effect, and to a less marked extent, the tin isotope effect, which is, of course, more complicated. Earlier observations of bands associated with tin compounds have been limited to a single band spectrum, namely, that developed under suitable conditions when tin or one of its compounds is introduced into a flame. Investigations up to the year 1912 are summarised by Kayser, who records grating measurements by Eder and Valenta and Von der Seipen. The bands of this spectrum degrade towards the red, and extend from λ 4766 to λ 3000.